Heat exchanger

ABSTRACT

A heat exchanger applied to a boiler that can improve heat transfer efficiency by reducing the distance between the heat exchange pipes while making a long heating water passage through heat exchange pipes, which can be easily manufactured. Additionally, the heat exchanger includes a heat exchange device, first and second subsidiary plates, and first and second end plates. The heat exchange device includes a plurality of heat exchange pipe units through which heating water passes and which are spaced apart from each other at regular intervals. The heat exchange pipe units are provided between a heating water inlet and a heating water outlet, and are formed of pipes having a rectangular cross-section of which a side coming in contact with the combustion gas has a width large than the height.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. application Ser.No. 12/664,818, filed Dec. 15, 2009, pending, which is the U.S. NationalStage application of International Application No. PCT/KR/002418, filedon Apr. 24, 2008, which claims priority to Korean Application No. KR10-2007-0058928 filed Jun. 15, 2007, disclosures of all of which areincorporated by reference herein in their entireties.

TECHNICAL FIELD

The present invention relates to a heat exchanger applied to a boiler,and more particularly, to a heat exchanger where heat transfer isefficiently performed between heating water passing through heatexchange pipes and exhaust gas.

BACKGROUND ART

Examples of a combustion device, which can heat heating water flowingthrough a heat exchange pipe in a combustion chamber by using a burneras widely known, may generally include a boiler, a water heater, and thelike.

That is, boilers, which are used in houses or public buildings, are usedfor heating or hot water. The water heater is used to quickly heat coldwater at a predetermined temperature in order to allow a user toconveniently use hot water.

The combustion device, such as the boiler and the water heater, includesa system that generally uses oil or gas as fuel and burns the fuel by aburner, heats water by using the heat of combustion generated in thecombustion process, and provides the heated water (hot water) accordingto user's needs.

The combustion device is provided with a heat exchanger so as to absorbthe heat of combustion generated from a burner. Various method ofimproving the heat transfer efficiency of the heat exchanger has beenproposed in the related art.

FIG. 1 is a schematic front view showing the structure of a heatexchanger in the related art, FIG. 2A is a detailed cross-sectional viewtaken along a line A-A of FIG. 1, and FIG. 2B is a detailedcross-sectional view taken along a line B-B of FIG. 1.

Referring to FIGS. 1 and 2, a heat exchanger 1 includes a heating waterinlet 10, a heat exchange device 20, and a heating water outlet 30.Heating water flows through the heating water inlet. The heat exchangedevice includes a plurality of heat exchange pipes 21, 22, 23, 24, and25. The surfaces of the heat exchange pipes come in contact withcombustion gas so that heat transfer is performed while heating waterflowing from the heating water inlet 10 passes through the heat exchangepipes. The heating water, which is heated while passing through the heatexchange pipes 21, 22, 23, 24, and 25, is discharged through the heatingwater outlet.

The heating water inlet 10 and the heat exchange pipes 21, 22, 23, 24,and 25, are connected to each other by pipe connectors 11. The heatingwater outlet 30 and the heat exchange pipes 21, 22, 23, 24, and 25 areconnected to each other by pipe connectors 31.

Each of the heat exchange pipes 21, 22, 23, 24, and 25 has asubstantially rectangular shape that has a large width and a smallheight in a longitudinal direction where combustion gas flows. The heatexchange pipes 21, 22, 23, 24, and 25 are spaced from each other by apredetermined distance, so that heat transfer is performed while thecombustion gas passes between the heat exchange pipes 21, 22, 23, 24,and 25.

The heat exchange pipes 21, 22, 23, 24, and 25 includes upper plates 21a, 22 a, 23 a, 24 a, and 25 a and lower plates 21 b, 22 b, 23 b, 24 b,and 25 b, respectively. The upper plates 21 a, 22 a, 23 a, 24 a, and 25a and the lower plates 21 b, 22 b, 23 b, 24 b, and 25 b are fixed toeach other at flanges thereof by welding.

Further, each of the pipe connectors 31, which connect the heat exchangepipes 21, 22, 23, 24, and 25, includes first and second connectingmembers 31 a and 31 b that have flanges bent in a lateral direction andare fixed to each other by welding (the pipe connectors 11 at theentrance of the heating water have the same structure).

DISCLOSURE OF INVENTION Technical Problem

However, in the heat exchanger having the above-mentioned structure, adistance between the heat exchange pipes is large due to the structuralcharacteristic of the heat exchange pipes that include the upper andlower plates and first and second connecting members. For this reason,there is a drawback in that heat transfer efficiency deteriorates.Further, there are problems in that it is difficult to actually applythe heat exchanger to a boiler because the manufacture of the heatexchanger is complicated and difficult.

Technical Solution

The present invention has been made to solve theabove-mentioned-problem, and an object of the present invention is toprovide a heat exchanger that can improve heat transfer efficiency byreducing distance between the heat exchange pipes while making theheating water passage passing through the heat exchange pipes be long,and can be easily manufactured.

In order to achieve the above-mentioned object, according to an aspectof the present invention, a heat exchanger includes a heat exchangedevice, first and second subsidiary plates, and first and second endplates. The heat exchange device includes a plurality of heat exchangepipe units through which heating water passes and which are spaced apartfrom each other at regular intervals. The heat exchange pipe units areprovided between a heating water inlet and a heating water outlet, andare formed of pipes having a rectangular cross-section of which a sidecoming in contact with the combustion gas has a width large than aheight. The first and second subsidiary plates are fixed to both ends ofthe heat exchange pipe units in order to maintain a distance between theplurality of heat exchange pipe units constant. The first and second endplates are fixed to the outer surfaces of the first and secondsubsidiary plates, respectively.

In this case, pipe insertion holes may be formed through the first andsecond subsidiary plates in a longitudinal direction of the first andsecond subsidiary plates. Both ends of the plurality of heat exchangepipe units may be fitted into the pipe insertion holes. Both ends of theheat exchange pipe units, first and second subsidiary plates, and firstand second end plates may be fixed by brazing welding, respectively.

Further, the plurality of heat exchange pipe units may form a series offlow passages of which flow directions are alternately changed inopposite directions while the heating water, which flows from the heatexchange pipe unit provided at one end, flows to the heat exchange pipeunit provided at the other end in opposite directions.

In this case, the heating water inlet may be formed through the firstend plate, and the heating water outlet may be formed through the secondend plate.

Furthermore, the heating water inlet may be formed on the outer surfaceof the heat exchange pipe unit into which heating water flows, and theheating water outlet may be formed on the outer surface of the heatexchange pipe unit from which heating water flows.

Meanwhile, the cross-sections of the plurality of heat exchange pipesmay be formed so that a distance between the heat exchange pipes at theentrance of the combustion gas is large and a distance between the heatexchange pipes at the exit of the combustion gas is small.

Advantageous Effects

As described in detail above, in the heat exchanger according to thepresent invention, it is possible to obtain advantages of improving heattransfer efficiency by reducing a distance between the heat exchangepipes while making the flow passage passing through the heat exchangepipes be long, and being easily manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing the structure of a heatexchanger in the related art;

FIG. 2A is a detailed cross-sectional view taken along a line A-A ofFIG. 1;

FIG. 2B is a detailed cross-sectional view taken along a line B-B ofFIG. 1;

FIG. 3 is an assembled perspective view of a heat exchanger according toan embodiment of the present invention;

FIG. 4 is an exploded perspective view of the heat exchanger shown inFIG. 3;

FIG. 5 is a cross-sectional view showing heating water passages of theheat exchanger shown in FIG. 3;

FIG. 6 is an assembled perspective view of a heat exchanger according toanother embodiment of the present invention;

FIG. 7 is a cross-sectional view showing heating water passages of theheat exchanger shown in FIG. 6;

FIG. 8 is a cross-sectional view of pipes of the heat exchange accordingto another embodiment of the present invention; and

FIG. 9 is a cross-sectional view of a heat exchange pipe according toanother embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The structure and operation of preferred embodiments of the presentinvention will be described in detail below with reference toaccompanying drawings.

FIG. 3 is an assembled perspective view of a heat exchanger according toan embodiment of the present invention, FIG. 4 is an explodedperspective view of the heat exchanger shown in FIG. 3, and FIG. 5 is across-sectional view showing heating water passages of the heatexchanger shown in FIG. 3.

A heat exchanger according to this embodiment includes a first end plate110, a first subsidiary plate 130, a heat exchange device 200, a secondend plate 310, and a second subsidiary plate 330. The first end plate isprovided near an entrance through which heating water flows, and has aheating water inlet 120. The first subsidiary plate is fixed to theinner surface of the first end plate 110. The heat exchange deviceincludes a plurality of heat exchange pipe units 210, 220, and 230 sothat heat is exchanged between the heating water and combustion gaswhile heating water flows in the heat exchange pipe units through theheating water inlet 120. The second end plate has a heating water outlet320 through which the heating water heated in the heat exchange device200 is discharged. The second subsidiary plate is fixed between theinner surface of the second end plate 310 and the heat exchange device200.

The first end plate 110 includes a flat part 110 a that closes one endsof the heat exchange pipes of the heat exchange device 200, and a bentpart 110 b that is bent from the lower end of the flat part 110 a so asto make the heating water to flow therethrough. The heating water inlet120 is formed at the bent part 110 b.

A plurality of pipe insertion holes 130 a and 330 a are formed throughthe first and second subsidiary plates 130 and 330 in a longitudinaldirection thereof at regular intervals, respectively, so that both endsof the pipes of the heat exchange pipe units 210, 220, and 230 areinserted into the pipe insertion holes.

Combustion gas passages 201 are formed between the heat exchange pipesof the heat exchange device 200 so as to be spaced apart from each otherat regular intervals so that combustion gas passes through thecombustion gas passages.

In this embodiment, the cross-section of the heat exchange pipe isformed in a rectangular shape so that the surface area of the heatexchange pipe coming in contact with combustion gas is increased.However, the shape of the cross-section is not limited thereto, and anyrectangular shape is possible as long as the heat exchange pipe has arectangular cross-section of which a side coming in contact with thecombustion gas has a width larger than the height. For example, each ofthe corners of the rectangular heat exchange pipe may have a roundedshape.

The heat exchange device 200 is provided with a first heat exchange pipeunit 210. The heating water, which flows from the heating water inlet120 formed at one end of the heat exchange device, passes through theheat exchange pipe unit.

One ends of two heat exchange pipes 211 and 212 of the first heatexchange pipe unit 210 are inserted into the pipe insertion holes 130 aof the first subsidiary plate 130, and the other ends thereof areinserted into the pipe insertion holes 330 a of the second subsidiaryplate 330.

The two heat exchange pipes 211 and 212 are spaced apart from each otherat regular intervals so that combustion gas can pass therebetween.

In this case, the heat exchange pipe 211 is formed by bending a largemetal plate so as to form a rectangular cross-section, caulking flanges211 f protruding from the side surface, and fixing the flanges bybrazing welding.

Flange insertion grooves 130 b and 330 b are formed in the pipeinsertion holes 130 a and 330 a of the first and second subsidiaryplates 130 and 330 so that the flanges 211 f of the heat exchange pipe211 are inserted into the flange insertion grooves.

If the protruding flanges 211 f are removed by a separate process, theflange insertion grooves 130 b and 330 b do not need to be formed.

The two heat exchange pipes 211 and 212 are connected to each other atpipe connectors 211 a and 212 a that are fanned at the other ends of theheat exchange pipes, so that the heating water in the lower heatexchange pipe 211 and the heating water in the upper heat exchange pipe212 are sent to a second heat exchange pipe unit 220 through pipeconnectors 212 b and 221 a.

The pipe connectors 211 a and 212 a protrude from the surface of theheat exchange pipe and are fixed to each other by welding. The shapesand fixing methods of pipe connectors 221 a, 221 b, 221 c, 222 a, 222 b,222 c, 231 a, 231 b, and 232 a to be described below, where pipes of thesecond and third heat exchange pipe units 220 and 230 are connected toeach other, are the same as described above.

According to this structure, since the distance between the two heatexchange pipes 211 and 212 can be decreased, it is possible to improveheat transfer efficiency. The structures of the second and third heatexchange pipe unit 220 and 230 to be described below are the same asdescribed above.

One ends of two heat exchange pipes 221 and 222 of the second heatexchange pipe unit 220 are inserted into the pipe insertion holes 130 aof the first subsidiary plate 130, and the other ends thereof areinserted into the pipe insertion holes 330 a of the second subsidiaryplate 330 so as to be disposed at regular intervals. The two heatexchange pipes 221 and 222 are connected to each other at pipeconnectors 221 b and 222 a that are formed at one ends of the heatexchange pipes. While heating water sent from the first heat exchangepipe unit 210 is supplied to two heat exchange pipes 221 and 222 andsent to the left side, heat is exchanged between the heating water andcombustion gas. Then, the heating water is sent to the third heatexchange pipe unit 230.

One ends of two heat exchange pipes 231 and 232 of the third heatexchange pipe unit 230 are inserted into the pipe insertion holes of thefirst subsidiary plate 130, and the other ends thereof are inserted intothe pipe insertion holes of the second subsidiary plate 330 so as to bedisposed at regular intervals. The two heat exchange pipes 231 and 232are connected to each other at pipe connectors 231 b and 232 a that areformed at one ends of the heat exchange pipes. While heating water sentfrom the second heat exchange pipe unit 220 is supplied to two heatexchange pipes 231 and 232 and sent to the right side, heat is exchangedbetween the heating water and combustion gas. Then, the heating water issent to places to be heated through the heating water outlet 320.

The second end plate 310 includes a flat part 310 a that closes one endsof the heat exchange pipes of the first and second heat exchange pipeunits 210 and 220, and a bent part 310 b that is bent from the upperportion of the flat part 310 a so as to make the heating water to flowtherethrough. The heating water outlet 320 is formed at the bent part310 b.

A method of fixing the heat exchange pipes to the first subsidiary plate130 and the first end plate 110, and a method of fixing the heatexchange pipes to the second subsidiary plate 330 and the second endplate 310 will be described.

Both ends of each heat exchange pipe are inserted into the pipeinsertion holes 130 a of the first subsidiary plate 130, and then thefirst end plate 110 comes in close contact with the outer surface of thefirst subsidiary plate. Then, brazing welding is performed at portionswhere the heat exchange pipes and the pipe insertion holes 130 a of thefirst subsidiary plate 130 come in contact with each other (a inenlarged portion of FIG. 5) and at portions where the first subsidiaryplate 130 and the first end plate 110 comes in contact with each other(b in enlarged portion of FIG. 5), thereby firmly fixing the pipes andthe plates.

A method of fixing the heat exchange pipes to the second subsidiaryplate 330 and the second end plate 310 also is the same as describedabove.

According to the above-mentioned structure, the heating water, which issent to the right side through the first heat exchange pipe unit 210, issent in opposite directions in the second and third heat exchange pipeunits 220 and the 230. Therefore, the length of the flow passage throughwhich heating water flows is increased, so that it is possible toimprove heat transfer efficiency.

A structure where heating water flows from the left side of the heatexchange pipe to the right side thereof has been exemplified in theembodiment.

A structure where heating water flows from the lower side of the heatexchange pipe to the upper side thereof will be described with referenceto FIGS. 6 and 7.

FIG. 6 is an assembled perspective view of a heat exchanger according toanother embodiment of the present invention, and FIG. 7 is across-sectional view showing heating water passages of the heatexchanger shown in FIG. 6.

A heat exchanger according to this embodiment includes a heat exchangedevice 500. The heat exchange device includes a plurality of heatexchange pipe units 510, 520, and 530 so that heat is exchanged betweenthe heating water and combustion gas while heating water flows in theheat exchange pipe units through a heating water inlet 420 and theheating water is then discharged through a heating water outlet 620.

The heating water inlet 420 is formed on a lower heat exchange pipe 511of a first heat exchange pipe unit 510, and the heating water outlet 620is formed on an upper heat exchange pipe 532 of a third heat exchangepipe unit 530.

Like the embodiment shown in FIGS. 3 to 5, any rectangular shape isapplied to each pipe of the heat exchange pipe units 510, 520, and 530as long as the heat exchange pipe has a rectangular cross-section ofwhich a side coming in contact with the combustion gas has a width largethan the height.

Further, the pipe connectors, which connect the pipes of the heatexchange pipe units 510, 520, and 530, are the same as those of theembodiment shown in FIGS. 3 to 5 except for the positions thereof.

A first subsidiary plate 430 and a first end plate 410 are sequentiallyfixed to one ends of the heat exchange pipe units 510, 520, and 530, anda second subsidiary plate 630 and a second end plate 610 aresequentially fixed to the other ends of the heat exchange pipe units510, 520, and 530.

Like the embodiment shown in FIGS. 3 to 5, pipe insertion holes 430 aand 630 a are formed through the first and second subsidiary plates 430and 630, respectively. The pipe insertion holes 430 a and 630 a arespaced apart from each other in a longitudinal direction thereof atregular intervals, so that the distance between the heat exchange pipesis maintained constant.

The first and second end plates 410 and 610 are formed in a flat shapeso as to close both ends of the heat exchange pipe units 510, 520, and530.

The heat exchange device 500 is provided with the first heat exchangepipe unit 510 through which heating water flowing through the heatingwater inlet 420 passes. The first heat exchange pipe unit 510 includestwo heat exchange pipes 511 and 512. The heat exchange pipes are fittedto the first and second subsidiary plates 430 and 630 and spaced apartfrom each other at regular intervals so that combustion gas can passtherebetween.

The heating water inlet 420 is connected to a pipe connector 511 a thatis formed on the lower surface of the lower heat exchange pipe 511 ofthe first heat exchange pipe unit 510.

The two heat exchange pipes 511 and 512 are connected to each other atpipe connectors 511 b and 512 a that are formed at one ends of the heatexchange pipes. The heating water in the lower heat exchange pipe 511and the heating water in an upper heat exchange pipe 512 are sent to thesecond heat exchange pipe unit 520.

The pipe connectors 511 a, 511 b, and 512 a protrude from the surface ofthe heat exchange pipes and are welded on the surface thereof,respectively. The shapes and fixing methods of pipe connectors(reference numerals are not given thereto) where pipes of the second andthird heat exchange pipe units 520 and 530 are connected to each otherare the same as described above.

The second heat exchange pipe unit 520 includes two heat exchange pipes521 and 522, and the heating water in the second heat exchange pipe unitflows in a direction opposite to the direction of the flow of theheating water in the first heat exchange pipe unit 510, that is, flowsto the left side.

The heating water passing through the second heat exchange pipe unit 520flows into the third heat exchange pipe unit 530. The third heatexchange pipe unit 530 includes two heat exchange pipes 531 and 532.Heating water flows from left side to the right side, and is dischargedthrough the heating water outlet 620 that is connected to the pipeconnector formed on the upper surface of the upper heat exchange pipe532.

FIG. 8 is a cross-sectional view of pipes of the heat exchange accordingto another embodiment of the present invention.

It is preferable that a distance between heat exchange pipes 711, 712,713, 714, 715, and 716 through which combustion gas passes is larger atthe entrance side 700 a as compared to that of at the exit side 700 b.That is, as shown in FIG. 8, the cross-section of each of the heatexchange pipes 711, 712, 713, 714, 715, and 716 has a trapezoid shape ina horizontal direction. Therefore, it can be seen that the distancebetween the heat exchange pipes 711, 712, 713, 714, 715, and 716 isdecreased from the entrance side 700 a toward the exit side 700 b.

In general, the temperature of combustion gas is high at the entrance ofthe heat exchange pipe, and is low at the exit of the heat exchangepipe. Therefore, the volume of the combustion gas is reduced as thecombustion gas comes to the exit of the heat exchange pipe. If thevolume of the combustion gas is reduced as described above and the crosssection area of the heat exchange pipe at the entrance is equal to thecross section area of the heat exchange pipe at the exit, the speed ofthe combustion gas is reduced, which cause the heat transfer efficiencyto deteriorate.

Therefore, if the combustion gas flows into the entrance side 700 ahaving the large area and then flows out from the exit side 700 b likethe structure of the heat exchange pipe of the present invention, it ispossible to maintain the speed of the combustion gas from the entranceside 700 a to the exit side 700 b. As a result, it is possible toimprove the heat transfer efficiency.

FIG. 9 is a cross-sectional view of pipes of the heat exchange accordingto another embodiment of the present invention.

As shown in FIG. 9A, a heat exchange pipe 811 may be formed by forming aflat plate in a substantially rectangular cross-sectional shape, makingflanges 811 a come in contact with each other and protrude in a lateraldirection, and fixing the flanges by caulking and brazing welding.

Further, in FIG. 9B, a heat exchange pipe 911 may be formed by forming aflat plate in a substantially rectangular cross-sectional shape, makingflanges 911 a come in contact with each other so that both ends of aflat plate overlap each other on the upper surface of the heat exchangepipe 911, and fixing the flanges by caulking and brazing welding.

The present invention has been described above in connection with theexemplary embodiments of the present invention. However, the embodimentsare illustrative, and it will be apparent to those skilled in the artthat various modifications and changes may be made thereto withoutdeparting from the scope and spirit of the invention.

1. A heat exchanger comprising: a heat exchange device including aplurality of heat exchange pipe units through which heating water passesand which are spaced apart from each other at regular intervals, theheat exchange pipe units being provided between a heating water inletand a heating water outlet, and being formed of pipes having arectangular cross-section of which a side coming in contact with thecombustion gas has a width large than a height; first and secondsubsidiary plates to which both ends of the heat exchange pipe units arefixed to constantly maintain a distance between the plurality of heatexchange pipe units; first and second end plates that are fixed to theouter surfaces of the first and second subsidiary plates, respectively;wherein pipe insertion holes are formed through the first and secondsubsidiary plates in a longitudinal direction of the first and secondsubsidiary plates, both ends of the plurality of heat exchange pipeunits are fitted into the pipe insertion holes, and both ends of theheat exchange pipe units, first and second subsidiary plates, and firstand second end plates are fixed by brazing welding, respectively; andwherein the heating water inlet is formed at the heat exchange pipe unitinto which heating water flows, and the heating water outlet is formedat the heat exchange pipe unit from which heating water flows.
 2. A heatexchanger comprising: a heat exchange device including a plurality ofheat exchange pipe units through which heating water passes and whichare spaced apart from each other at regular intervals, the heat exchangepipe units being provided between a heating water inlet and a heatingwater outlet, and being formed of pipes having a rectangularcross-section of which a side coming in contact with the combustion gashas a width large than a height; first and second subsidiary plates towhich both ends of the heat exchange pipe units are fixed to constantlymaintain a distance between the plurality of heat exchange pipe units;first and second end plates that are fixed to the outer surfaces of thefirst and second subsidiary plates, respectively; wherein the pluralityof heat exchange pipe units forms a series of flow passages of whichflow directions are alternately changed in opposite directions while theheating water, which flows from the heat exchange pipe unit provided atone end, flows to the heat exchange pipe unit provided at the other end;and wherein the heating water inlet is formed at the heat exchange pipeunit into which heating water flows, and the heating water outlet isformed at the heat exchange pipe unit from which heating water flows.